The sentence you flagged at the end of the update is the right thing to be nervous about.
Here's how the two activities differ. Ongoing investor relations for people who are already invested covers reporting on performance, sending distribution notices, delivering K-1s, answering questions about an existing position, keeping records current. That's servicing an existing relationship, and it's routinely done by employees, property managers, and outsourced IR firms.
Soliciting investment is different. Offering a new deal, describing terms, pitching, screening interested investors, following up with prospects. In the US, being compensated for that activity, and especially being compensated based on how much money comes in, is the area that broker-dealer registration rules are built around. Whether any specific arrangement crosses that line depends on facts and on state law as well as federal, and it's a question for a securities attorney rather than a forum. That's the one sentence of legal caution I'll give you, and you should get it answered before the first invoice.
What this means practically: your flat monthly fee, unconnected to any raise, is a much cleaner starting point than a percentage. Keep new-offering material out of the update you write and let the sponsor send that separately from his own address.
On the phone question, the answer isn't yes or no, it's about scope. Answering "when does the March distribution hit" is servicing. An LP steering the call toward the next deal and you continuing the conversation is where the character of the call changes, and the useful habit is a hand-off line back to the sponsor. Also get your engagement letter to say who approves the numbers you publish, because you'll be writing them and he'll be responsible for them.